What you are seeing is most likely something spilled and has now run down along the inside of the outer glass panel. There is no seal that has gone bad, as oven doors are open on the inside with vents along the top and bottom. This allows for air to flow and to help keep the outer surface of the glass cooler to the touch. The doors can usually be taken apart with not much effort by removing any trim screws and separating the door panels. This is rather generic information without a specific model number available to reference. Clean the spill and put it back together.